J. Ruste

Massively parallel molecular dynamics simulations with EAM potentials

Abstract Molecular dynamics of cascades in pure iron and iron–copper alloys using embedded atom method type of interatomic potentials are presented. Reliable simulations of radiation damage at the atomic scale with high energy Primary Knocked Atoms (PKA) need systems with large numbers of particles and very long computational time. To perform the simulation in a reasonable amount of time high-performance computer systems such as massively parallel machines need to be used. This paper presents the parallelisation strategy applied to a serial classical Molecular Dynamics code: DYMOKA. The original sequential Fortran code CDCMD from the University of Connecticut was first improved algorithmically by applying a link cell method for the neighbour list construction of the Verlet list, resulting in a fully linear algorithm. The parallelisation strategy adopted is a multidimensional domain decomposition of the simulation box using a link cell method and a Verlet list method for each subdomain independently. The p...

Simulation of Irradiation Effects in Reactor Pressure Vessel Steels: the Reactor for Virtual Experiments (REVE) Project

Components of commercial nuclear reactors are subjected to neutron bombardments that can modify their mechanical properties. Prediction of in-service and post-service behaviors generally requires irradiation in so-called “test reactors” as well as subsequent mechanical testing in specialized hot cell facilities. However, the use of these research facilities is becoming more problematic, in particular due to increasing costs and decreasing availability. One way of partially mitigating these problems is to complement the empirical approach by developing tools for numerical simulation of irradiation effects in materials. The development of such tools is clearly an ambitious task that will require a long-term international collaborative effort. In this paper, we present an outline of the Reactor for Virtual Experiments (REVE) project, a collaborative European and American effort aimed at developing quantitative simulations of irradiation effects in materials. The first demonstration phase of REVE will target embrittlement of reactor pressure vessel (RPV) steels, since the effects and mechanisms of irradiation damage in this material are relatively well understood and many modeling tools have been developed or are under development in this field. As for any experiment, the input variables of the REVE simulation will be the neutron spectrum, time and temperature of irradiation, the alloy composition (e.g., Cu, Ni, Mn, and C contents) and microstructure and the unirradiated mechanical properties. The simulations will predict the irradiation-induced increases of yield stress and Charpy transition temperature as well as the decrease of toughness due to the concomitant evolution of the microstructure.

Computer simulations study of iron–copper alloy

Abstract The vessel steels of pressurised water reactors are embrittled by neutron irradiation. The changes of mechanical properties are commonly supposed to result from the formation of point defects, dislocation loops, voids and Cu-rich precipitates. The composition of such precipitates, specially the existence of vacancies, is not accessible through experiments. It is suggested that two mechanisms promote the formation of Cu-rich features in pressure vessel steels during neutron irradiation. When the Cu content is lower than 0.1%, solute-rich atmospheres can be formed in displacement cascades. For higher Cu contents, in addition to the latter phenomenon, a mechanism of accelerated precipitation can also induce the formation of Cu-rich clusters or precipitates. In order to understand all the mechanisms, Molecular Dynamics and Monte Carlo simulations have been carried out in pure Fe, and Fe–Cu alloys. Inter-atomic potentials of the Embedded Atom Method type, found in literature for pure Fe and pure Cu we...

Quantitative Microanalysis of Low Concentrations of Carbon in Steels

Conditions of quantitative X-ray microanalysis of carbon in industrial steels are given. The different problems are described and a solution is proposed for each of them. Examples of applications are given.